| Title | EXPERIMENTAL AND MODELING STUDY OF THE SOIL-ATMOSPHERE INTERACTION AND THE UNSATURATED WATER FLOW TO ESTIMATE THE RECHARGE OF A PHREATIC AQUIFER |
| Abstract | The aquifer system, which is the resource of water for the city of Milano (Italy), is a multilayered aquifer, characterized by sandy and sandy-gravel units, connected by discontinuous aquitards. The recharge area of the phreatic aquifer is close to the prealpine area, some tens of kilometers north of the city; nevertheless the local recharge given by rain infiltration through the soil is not negligible and contributes to the mass balance of the aquifer. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone; the water table in this area lies about 15 m below the ground surface. Standard meteorological data (atmospheric pressure, rainfall, humidity, wind velocity and air temperature) were collected, along with incident and net radiation, to evaluate potential and actual evaporation from the bare soil using three methods (Bowen ratio, Penman, and Hamon equations). Simultaneously, the volumetric soil water content at different depths down to 76 cm was measured with time domain reflectrometry probes. A finite-difference model, which solves the one-dimensional Richards equation in transient conditions, was developed to simulate the flow through the unsaturated zone, to evaluate the characteristic time of recharge and the mass balance. The water flow rate through the ground surface was assigned as the upper boundary condition and was evaluated from the mass and energy balance at the atmosphere-soil interface with different approaches based on the meteorological data and the actual soil water content. The lower boundary condition is given by the saturation condition at the water table. Characteristic retention curves were estimated in laboratory using Richards apparatus. In order to calibrate the model, the numerical results were compared with experimental data for two different periods: A dry period (July 2001) and a wet period (October 2001). Finally, the calibrated model was used to simulate the infiltration and the flow through the unsaturated zone for a 15-year-long period (1988-2003) and to estimate the total phreatic aquifer recharge. Moreover, the time lag between a variation of the infiltration/exfiltration rate and the corresponding variation of the recharge rate was evaluated; the values of the delay time of recharge are longer than those computed with models that approximate the transmission zone as a unique cell. |
| Source | Journal of hydrologic engineering 12 (6), pp. 573–584 |
| Journal | Journal of hydrologic engineering |
| Editor | The Society,, New York, NY, Stati Uniti d'America |
| Year | 2007 |
| Type | Articolo in rivista |
| DOI | 10.1061/(ASCE)1084-0699(2007)12:6(573) |
| Authors | ROMANO E. (1); GIUDICI M. (2) |
| Text | 42150 2007 10.1061/ ASCE 1084 0699 2007 12 6 573 ISI Web of Science WOS 000250317600003 EXPERIMENTAL AND MODELING STUDY OF THE SOIL ATMOSPHERE INTERACTION AND THE UNSATURATED WATER FLOW TO ESTIMATE THE RECHARGE OF A PHREATIC AQUIFER ROMANO E. 1 ; GIUDICI M. 2 1 Consiglio Nazionale delle Ricerche, Istituto di Ricerca sulle Acque, via Reno 1, 00198 Roma, Italy; 2 Dipt. di Scienze della Terra, Univ. degli Studi di Milano, Sezione di Geofisica, via Cicognara 7, 20129 Milano, Italy The aquifer system, which is the resource of water for the city of Milano Italy , is a multilayered aquifer, characterized by sandy and sandy gravel units, connected by discontinuous aquitards. The recharge area of the phreatic aquifer is close to the prealpine area, some tens of kilometers north of the city; nevertheless the local recharge given by rain infiltration through the soil is not negligible and contributes to the mass balance of the aquifer. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone; the water table in this area lies about 15 m below the ground surface. Standard meteorological data atmospheric pressure, rainfall, humidity, wind velocity and air temperature were collected, along with incident and net radiation, to evaluate potential and actual evaporation from the bare soil using three methods Bowen ratio, Penman, and Hamon equations . Simultaneously, the volumetric soil water content at different depths down to 76 cm was measured with time domain reflectrometry probes. A finite difference model, which solves the one dimensional Richards equation in transient conditions, was developed to simulate the flow through the unsaturated zone, to evaluate the characteristic time of recharge and the mass balance. The water flow rate through the ground surface was assigned as the upper boundary condition and was evaluated from the mass and energy balance at the atmosphere soil interface with different approaches based on the meteorological data and the actual soil water content. The lower boundary condition is given by the saturation condition at the water table. Characteristic retention curves were estimated in laboratory using Richards apparatus. In order to calibrate the model, the numerical results were compared with experimental data for two different periods A dry period July 2001 and a wet period October 2001 . Finally, the calibrated model was used to simulate the infiltration and the flow through the unsaturated zone for a 15 year long period 1988 2003 and to estimate the total phreatic aquifer recharge. Moreover, the time lag between a variation of the infiltration/exfiltration rate and the corresponding variation of the recharge rate was evaluated; the values of the delay time of recharge are longer than those computed with models that approximate the transmission zone as a unique cell. 12 Articolo Pubblicato 2007_Journal_of_Hydrologic_Engineering_Romano_and_Giudici_Experimental_and_Modeling_Study_of_the_Soil_Atmosphere.pdf Articolo in rivista The Society, 1084 0699 Journal of hydrologic engineering Journal of hydrologic engineering J. hydrol. eng. Journal of hydrologic engineering Hydrologic engineering ASCE journal of hydrologic engineering emanuele.romano ROMANO EMANUELE TA.P02.009.002 Effetti dei cambiamenti climatici sulla componente terrestre del ciclo idrologico |
